Gut-kidney crosstalk in septic acute kidney injury

Investigating gut microbiota-blood and urine metabolite correlations in early sepsis-induced acute kidney injury: insights from targeted KEGG analyses

Background

The interplay between gut microbiota and metabolites in the early stages of sepsis-induced acute kidney injury (SA-AKI) is not yet clearly understood. This study explores the characteristics and interactions of gut microbiota, and blood and urinary metabolites in patients with SA-AKI.

Methods

Utilizing a prospective observational approach, we conducted comparative analyses of gut microbiota and metabolites via metabolomics and metagenomics in individuals diagnosed with SA-AKI compared to those without AKI (NCT06197828). Pearson correlations were used to identify associations between microbiota, metabolites, and clinical indicators. The Comprehensive Antibiotic Resistance Database was employed to detect antibiotic resistance genes (ARGs), while Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways informed on metabolic processes and microbial resistance patterns.

Results

Our study included analysis of four patients with SA-AKI and five without AKI. Significant disparities in bacterial composition were observed, illustrated by diversity indices (Shannon index: 2.0 ± 0.4 vs. 1.4 ± 0.6, P = 0.230; Simpson index: 0.8 ± 0.1 vs. 0.6 ± 0.2, P = 0.494) between the SA-AKI group and the non-AKI group. N6, N6, N6-Trimethyl-L-lysine was detected in both blood and urine metabolites, and also showed significant correlations with specific gut microbiota (Campylobacter hominis and Bacteroides caccae, R > 0, P < 0.05). Both blood and urine metabolites were enriched in the lysine degradation pathway. We also identified the citrate cycle (TCA cycle) as a KEGG pathway enriched in sets of differentially expressed ARGs in the gut microbiota, which exhibits an association with lysine degradation.

Conclusions

Significant differences in gut microbiota and metabolites were observed between the SA-AKI and non-AKI groups, uncovering potential biomarkers and metabolic changes linked to SA-AKI. The lysine degradation pathway may serve as a crucial link connecting gut microbiota and metabolites.

Positive pathogens in stool could predict the clinical outcomes of sepsis-associated acute kidney injury in critical ill patient

In this study, we sought to evaluate the influence of positive pathogens in stool (PPS) on clinical outcomes in critical ill patients with Sepsis-associated acute kidney injury (S-AKI) from intensive care unit. Our sample consisted of 7338 patients, of whom 752 (10.25%) had PPS. We found that the presence of Clostridium difficile (C. difficile) and protists in stool samples was correlated with survival during hospitalization, as well as 30-day and 90-day survival. Interestingly, there was no significant difference in overall survival and 30-day in-hospital survival between the PPS group and the negative pathogens in stool (NPS) control group. However, the cumulative incidence of 90-day infection-related mortality was significantly higher in the PPS group (53 vs. 48%, P = 0.022), particularly in patients with C. difficile in their stool specimens. After adjusting for propensity scores, the results also have statistical significance. These findings suggest that PPS may affect the 90-days survival outcomes of S-AKI, particularly in patients with C. difficile and protists in their stool samples. Further research is warranted to further explore these associations.

Pellino1 orchestrates gut-kidney axis to perpetuate septic acute kidney injury through activation of STING pathway and NLRP3 inflammasome

AIMS

Intestinal barrier dysfunction is the initial and propagable factor of sepsis in which acute kidney injury (AKI) has been considered as a common life-threatening complication. Our recent study identifies the regulatory role of Pellino1 in tubular death under inflammatory conditions in vitro. The objective of our current study is to explore the impact of Pellino1 on gut-kidney axis during septic AKI and uncover the molecular mechanism (s) underlying this process.

MATERIALS AND METHODS

Immunohistochemistry (IHC) was conducted to evaluate Pellino1 and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) levels in renal biopsies from critically ill patients with a clinical diagnosis of sepsis. Functional and mechanistic studies were characterized in septic models of the Peli-knockout (Peli1-/-) mice by histopathological staining, enzyme-linked immunosorbent assay (ELISA), flow cytometry, immunofluorescence, biochemical detection, CRISPR/Cas9-mediated gene editing and intestinal organoid.

KEY FINDINGS

Pellino1, together with NLRP3, are highly expressed in renal biopsies from critically ill patients diagnosed with sepsis and kidney tissues of septic mice. The Peli1-/- mice with sepsis become less prone to develop AKI and have markedly compromised NLRP3 activation in kidney. Loss of Peli1 endows septic mice refractory to intestinal inflammation, barrier permeability and enterocyte apoptosis that requires stimulator of interferons genes (STING) pathway. Administration of STING agonist DMXAA deteriorates AKI and mortality of septic Peli1-/- mice in the presence of kidney-specific NLRP3 reconstitution.

SIGNIFICANCE

Our studies suggest that Pellino1 has a principal role in orchestrating gut homeostasis towards renal pathophysiology, thus providing a potential therapeutic target for septic AKI.

Ferroptosis: a potential bridge linking gut microbiota and chronic kidney disease

Ferroptosis is a novel form of lipid peroxidation-driven, iron-dependent programmed cell death. Various metabolic pathways, including those involved in lipid and iron metabolism, contribute to ferroptosis regulation. The gut microbiota not only supplies nutrients and energy to the host, but also plays a crucial role in immune modulation and metabolic balance. In this review, we explore the metabolic pathways associated with ferroptosis and the impact of the gut microbiota on host metabolism. We subsequently summarize recent studies on the influence and regulation of ferroptosis by the gut microbiota and discuss potential mechanisms through which the gut microbiota affects ferroptosis. Additionally, we conduct a bibliometric analysis of the relationship between the gut microbiota and ferroptosis in the context of chronic kidney disease. This analysis can provide new insights into the current research status and future of ferroptosis and the gut microbiota.

EFFECTS OF HYPERBARIC OXYGEN THERAPY ON INTESTINAL ISCHEMIA-REPERFUSION AND ITS MECHANISM

ABSTRACT

Ischemia can cause reversible or irreversible cell or tissue damage, and reperfusion after ischemia not only has no therapeutic effect but also aggravates cell damage. Notably, gut tissue is highly susceptible to ischemia-reperfusion (IR) injury under many adverse health conditions. Intestinal IR (IIR) is an important pathophysiological process in critical clinical diseases. Therefore, it is necessary to identify better therapeutic methods for relieving intestinal ischemia and hypoxia. Hyperbaric oxygenation refers to the intermittent inhalation of 100% oxygen in an environment greater than 1 atm pressure, which can better increase the oxygen level in the tissue and change the inflammatory pathway. Currently, it can have a positive effect on hypoxia and ischemic diseases. Related studies have suggested that hyperbaric oxygen can significantly reduce ischemia-hypoxic injury to the brain, spinal cord, kidney, and myocardium. This article reviews the pathogenesis of IR and the current treatment measures, and further points out that hyperbaric oxygen has a better effect in IR. We found that not only improved hypoxia but also regulated IR induced injury in a certain way. From the perspective of clinical application, these changes and the application of hyperbaric oxygen therapy have important implications for treatment, especially IIR.

Septic acute kidney injury and gut microbiome: Should we change our approach?

Incidence of acute kidney injury (AKI) remained relatively stable over the last decade and the adjusted risks for it and mortality are similar across different continents and regions. Also, the mortality of septic-AKI can reach 70% in critically-ill patients. These sole facts can give rise to a question: is there something we do not understand yet? Currently, there are no specific therapies for septic AKI and the treatment aims only to maintain the mean arterial pressure over 65mmHg by ensuring a good fluid resuscitation and by using vasopressors, along with antibiotics. On the other hand, there is an increased concern about the different hemodynamic changes in septic AKI versus other forms and the link between the gut microbiome and the severity of septic AKI. Fortunately, progress has been made in the form of administration of pre- and probiotics, short chain fatty acids (SCFA), especially acetate, and also broad-spectrum antibiotics or selective decontaminants of the digestive tract in a successful attempt to modulate the microbial flora and to decrease both the severity of AKI and mortality. In conclusion, septic-AKI is a severe form of kidney injury, with particular hemodynamic changes and with a strong link between the kidney and the gut microbiome. By modulating the immune response we could not only treat but also prevent severe forms. The most difficult part is to categorize patients and to better understand the key mechanisms of inflammation and cellular adaptation to the injury, as these mechanisms can serve in the future as target therapies.

Nutrition in Critically Ill Children with AKI on Continuous RRT: Consensus Recommendations

BACKGROUND

Nutrition plays a vital role in the outcome of critically ill children, particularly those with AKI. Currently, there are no established guidelines for children with AKI treated with continuous RRT (CRRT). A thorough understanding of the metabolic changes and nutritional challenges in AKI and CRRT is required. Our objective was to create clinical practice points for nutritional assessment and management in critically ill children with AKI receiving CRRT.

METHODS

PubMed, MEDLINE, Cochrane, and Embase databases were searched for articles related to the topic. Expertise of the authors and a consensus of the workgroup were additional sources of data in the article. Available articles on nutrition therapy in pediatric patients receiving CRRT through January 2023.

RESULTS

On the basis of the literature review, the current evidence base was examined by a panel of experts in pediatric nephrology and nutrition. The panel used the literature review as well as their expertise to formulate clinical practice points. The modified Delphi method was used to identify and refine clinical practice points.

CONCLUSIONS

Forty-four clinical practice points are provided on nutrition assessment, determining energy needs, and nutrient intake in children with AKI and on CRRT on the basis of the existing literature and expert opinions of a multidisciplinary panel.

Serum total protein-to-albumin ratio predicts risk of death in septic acute kidney injury patients: A cohort study

OBJECTIVE

Sepsis is the leading cause of acute kidney injury (AKI). Increasing evidence shows that serum total protein-to-albumin ratio (TAR) could serve as an inflammation- and nutrition-based prognostic marker in various diseases. The purpose of this study was to assess the prognostic value of TAR in predicting the clinical outcomes of septic AKI patients.

METHODS

We retrospectively enrolled septic AKI patients between August 2015 and August 2022 at West China Hospital of Sichuan University. Patients admitted between August 2015 and August 2021 were defined as the original cohort. The primary outcomes were 30-day and 90-day all-cause mortality of septic AKI patients. The secondary outcomes were septic shock, transfer to the intensive care unit, mechanical ventilation, requirement for renal replacement therapy, and stage 3 AKI. The utility of TAR was further verified in a validation cohort of septic AKI patients admitted between September 2021 and August 2022.

RESULTS

In the original cohort, a total of 309 eligible patients with a median age of 58 years were enrolled, of which 70.2 % were males. In multivariate Cox analysis, after adjustments for age, sex, and other confounding factors, higher TAR at admission was associated with an increased risk of 30-day and 90-day all-cause mortality in septic AKI patients (HR 1.91, 95 % CI 1.18-3.09, P = 0.008; HR 1.54, 95 % CI 1.01-2.34, P = 0.043, respectively). Subgroup analysis revealed no significant interactions in most strata. TAR at AKI diagnosis or discharge was not significantly related to 30-day (P = 0.120 and 0.153, respectively) or 90-day mortality (P = 0.147 and 0.124, respectively). We found no relationship between baseline TAR and septic shock, transfer to the intensive care unit, mechanical ventilation, requirement for renal replacement therapy, or stage 3 AKI (all P > 0.05). In the validation cohort of 81 septic AKI patients, TAR at admission remained a significant prognosticator for 30-day and 90-day mortality (HR 4.367, 95 % CI 1.20-15.87, P = 0.025; HR 4.237, 95 % CI 1.59-11.27, P = 0.004).

CONCLUSIONS

TAR at admission is an independent risk factor for 30-day and 90-day mortality in septic AKI patients and could be used as a convenient and economic septic AKI prognostic indicator.

Gut-derived 4-hydroxyphenylacetic acid attenuates sepsis-induced acute kidney injury by upregulating ARC to inhibit necroptosis

BACKGROUND

Studies have found that the plasma content of gut-derived 4-hydroxyphenylacetic acid (4-HPA) was significantly increased in septic patients. However, the mechanism of 4-HPA elevation during sepsis and its relationship with sepsis-induced acute kidney injury (SAKI) remain unclear.

METHODS

Cecal ligation and puncture (CLP) was performed in C57BL/6 mice to establish the SAKI animal model. Human renal tubular epithelial (HK-2) cells stimulated with lipopolysaccharide were used to establish the SAKI cell model. The widely targeted metabolomics was applied to analyze the renal metabolite changes after CLP. Proteomics was used to explore potential target proteins regulated by 4-HPA. The blood sample of clinical sepsis patients was collected to examine the 4-HPA content.

RESULTS

We found that renal gut-derived 4-HPA levels were significantly increased after CLP. The high permeability of intestinal barrier after sepsis contributed to the dramatic increase of renal 4-HPA. Intriguingly, we demonstrated that exogenous 4-HPA administration could further significantly reduce CLP-induced increases in serum creatinine, urea nitrogen, and cystatin C, inhibit renal pathological damage and apoptosis, and improve the survival of mice. Mechanistically, 4-HPA inhibited necroptosis in renal tubular epithelial cells by upregulating the protein expression of apoptosis repressor with caspase recruitment domain (ARC) and enhancing the interaction between ARC and receptor-interacting protein kinase 1 (RIPK1).

CONCLUSIONS

The increase of gut-derived 4-HPA in the kidney after sepsis could play a protective effect in SAKI by upregulating ARC to inhibit necroptosis.

Nutritional management of children with acute kidney injury-clinical practice recommendations from the Pediatric Renal Nutrition Taskforce

The nutritional management of children with acute kidney injury (AKI) is complex. The dynamic nature of AKI necessitates frequent nutritional assessments and adjustments in management. Dietitians providing medical nutrition therapies to this patient population must consider the interaction of medical treatments and AKI status to effectively support both the nutrition status of patients with AKI as well as limit adverse metabolic derangements associated with inappropriately prescribed nutrition support. The Pediatric Renal Nutrition Taskforce (PRNT), an international team of pediatric renal dietitians and pediatric nephrologists, has developed clinical practice recommendations (CPR) for the nutritional management of children with AKI. We address the need for intensive collaboration between dietitians and physicians so that nutritional management is optimized in line with AKI medical treatments. We focus on key challenges faced by dietitians regarding nutrition assessment. Furthermore, we address how nutrition support should be provided to children with AKI while taking into account the effect of various medical treatment modalities of AKI on nutritional needs. Given the poor quality of evidence available, a Delphi survey was conducted to seek consensus from international experts. Statements with a low grade or those that are opinion-based must be carefully considered and adapted to individual patient needs, based on the clinical judgment of the treating physician and dietitian. Research recommendations are provided. CPRs will be regularly audited and updated by the PRNT.

Novel MAGL Inhibitors Alleviate LPS-Induced Acute Kidney Injury by Inhibiting NLRP3 Inflammatory Vesicles, Modulating Intestinal Flora, Repairing the Intestinal Barrier, and Interfering with Serum Metabolism

Acute kidney injury (AKI) is a complication of a wide range of serious illnesses for which there is still no better therapeutic agent. We demonstrated that M-18C has a favorable inhibitory effect on monoacylglycerol lipase (MAGL), and several studies have demonstrated that nerve inflammation could be effectively alleviated by inhibiting MAGL, suggesting that M-18C has good anti-inflammatory activity. In this study, we investigated the effect of M-18C on LPS-induced acute kidney injury (AKI), both in vivo and in vitro, by using liquid chromatography-mass spectrometry (LC-MS), 16S rRNA gene sequencing, Western blot, and immunohistochemistry. The results showed that both in vivo and in vitro M-18C reduced the release of TNF-α and IL-1β by inhibiting the expression of NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) and apoptosis-associated speck-like protein containing a CARD (ASC) protein; in addition, M-18C was able to intervene in LPS-induced AKI by ameliorating renal pathological injury, repairing the intestinal barrier, and regulating gut bacterial flora and serum metabolism. In conclusion, this study suggests that M-18C has the potential to be a new drug for the treatment of AKI.

CHIP protects against septic acute kidney injury by inhibiting NLRP3-mediated pyroptosis

Septic acute kidney injury (S-AKI), the most common type of acute kidney injury (AKI), is intimately related to pyroptosis and oxidative stress in its pathogenesis. Carboxy-terminus of Hsc70-interacting protein (CHIP), a U-box E3 ligase, modulates oxidative stress by degrading its targeted proteins. The role of CHIP in S-AKI and its relevance with pyroptosis have not been investigated. In this study, we showed that CHIP was downregulated in renal proximal tubular cells in lipopolysaccharide (LPS)-induced S-AKI. Besides, the extent of redox injuries in S-AKI was attenuated by CHIP overexpression or activation but accentuated by CHIP gene disruption. Mechanistically, our work demonstrated that CHIP interacted with and ubiquitinated NLRP3 to promote its proteasomal degradation, leading to the inhibition of NLRP3/ACS inflammasome-mediated pyroptosis. In summary, this study revealed that CHIP ubiquitinated NLRP3 to alleviate pyroptosis in septic renal injuries, suggesting that CHIP might be a potential therapeutic target for S-AKI.

Protein modification by short-chain fatty acid metabolites in sepsis: a comprehensive review

Sepsis is a major life-threatening syndrome of organ dysfunction caused by a dysregulated host response due to infection. Dysregulated immunometabolism is fundamental to the onset of sepsis. Particularly, short-chain fatty acids (SCFAs) are gut microbes derived metabolites serving to drive the communication between gut microbes and the immune system, thereby exerting a profound influence on the pathophysiology of sepsis. Protein post-translational modifications (PTMs) have emerged as key players in shaping protein function, offering novel insights into the intricate connections between metabolism and phenotype regulation that characterize sepsis. Accumulating evidence from recent studies suggests that SCFAs can mediate various PTM-dependent mechanisms, modulating protein activity and influencing cellular signaling events in sepsis. This comprehensive review discusses the roles of SCFAs metabolism in sepsis associated inflammatory and immunosuppressive disorders while highlights recent advancements in SCFAs-mediated lysine acylation modifications, such as substrate supplement and enzyme regulation, which may provide new pharmacological targets for the treatment of sepsis.

Factors associated with gastrointestinal dysmotility in critically ill patients

Critical illness may disrupt nutritional, protective, immune, and endocrine functions of the gastrointestinal tract, leading to a state of gastrointestinal dysmotility. We aimed to identify factors associated with the occurrence of gastrointestinal dysmotility in critically ill patients. A cross-sectional retrospective study was conducted, using patient files as a source of data. The study included 185 critically ill patients treated in the intensive care unit of the University Clinical Center, Kragujevac, Serbia, from January 1, 2016, to January 1, 2022. Significant risk factors associated with some form of gastrointestinal dysmotility were acute kidney injury (with paralytic ileus, nausea, vomiting, and constipation), recent abdominal surgery (with ileus, nausea, vomiting, and constipation), mechanical ventilation (with ileus, and nausea), age (with ileus and constipation), and use of certain medication such as opioids (with ileus, gastro-esophageal reflux, nausea, vomiting, and constipation), antidepressants (with ileus, nausea, and vomiting), and antidiabetics (with ileus). On the other hand, Charlson comorbidity index had divergent effects, depending on the form of gastrointestinal dysmotility: it increased the risk of gastro-esophageal reflux but protected against ileus, nausea, and vomiting. In clonclusion, recognition of factors associated with gastrointestinal dysmotility should initiate preventative measures and, thus, accelerate the recovery of critically ill.

Nutrition for critically ill children and neonates requiring dialysis: Application of clinical practice recommendations

Approximately 30% of all children and neonates admitted to the intensive care unit (ICU) experience acute kidney injury (AKI). Children with AKI are largely poorly fed and experience high rates of malnutrition. Nutrition prescription and provision are exceptionally challenging for critically ill neonates, infants, and children with AKI given the dynamic nature of AKI and its respective treatment modalities. Managing the nutrition prescription of critically ill neonates, infants, and children with AKI requires nutrition support clinicians to have a high-level understanding of the various treatment modalities for AKI, which can affect the patient's protein, fluid, electrolyte, and mineral needs. Accurate and timely nutrition assessment in critically ill neonates and children with AKI can be flawed owing to difficulty obtaining accurate anthropometric parameters. Recently, the Pediatric Renal Nutrition Taskforce introduced clinical practice recommendations for the nutrition management of children with AKI. In this review, we will discuss the practical implications of these recent guidelines and work to bridge the knowledge and practice gaps for pediatric and neonatal nutrition support clinicians providing nutrition therapy for patients with AKI in the ICU. We also appraise special nutrition-related considerations for neonates with AKI given newer available renal replacement treatment modalities.

Probiotics in septic acute kidney injury, a double blind, randomized control trial

INTRODUCTION

During acute kidney injury (AKI) due to sepsis, the intestinal microbiota changes to dysbiosis, which affects the kidney function recovery (KFR) and amplifies the injury. Therefore, the administration of probiotics could improve dysbiosis and thereby increase the probability of KFR.

METHODS

In this double-blind clinical trial, patients with AKI associated with sepsis were randomized (1:1) to receive probiotics or placebo for 7 consecutive days, with the objectives of evaluate the effect on KFR, mortality, kidney replacement therapy (KRT), urea, urine volume, serum electrolytes and adverse events at day 7.

RESULTS

From February 2019 to March 2022, a total of 92 patients were randomized, 48 to the Probiotic and 44 to Placebo group. When comparing with placebo, those in the Probiotics did not observe a higher KFR (HR 0.93, 0.52-1.68, p = 0.81), nor was there a benefit in mortality at 6 months (95% CI 0.32-1.04, p = 0.06). With probiotics, urea values decreased significantly, an event not observed with placebo (from 154 to 80 mg/dl, p = 0.04 and from 130 to 109 mg/dl, p = 0.09, respectively). Urinary volume, need for KRT, electrolyte abnormalities, and adverse events were similar between groups. (ClinicalTrial.gov NCT03877081) (registered 03/15/2019).

CONCLUSION

In AKI related to sepsis, probiotics for 7 consecutive days did not increase the probability of KFR, nor did other variables related to clinical improvement, although they were safe.

Evaluation of the Efficiency of TIMP-2 as a Biomarker for Acute Kidney Injury in Sepsis

The aim of this study was to evaluate the biomarker potential of TIMP-2 in septic-induced acute kidney injury (AKI). Healthy male rats (n=56, age 8-10 weeks, body weight 250-300 g) were randomized into 3 groups: controls (intact rats, n=6), sham-operated (SO, n=24), and sepsis model (cecum ligation and perforation, CLP, n=24). Thirty minutes before and 6, 12, 24, and 48 h after surgery, blood samples were collected to measure serum creatinine, blood urea nitrogen (BUN), and TIMP-2 and the kidneys were isolated for histopathological analysis and Western blotting. The key sepsis-related genes were screened through bioinformatics analysis. In 24 and 48 h after surgery, 2 rats in the SO group reached the diagnostic criteria of AKI (increased levels of serum creatinine and BUN). In the CLP group, serum creatinine in 6 h after the surgery was slightly higher than 30 min before the surgery, but this change did not meet the diagnostic criteria for AKI. In the CLP group, BUN was normal 6 h after the surgery, but increased after 12 h. In more than 50% rats of the CLP group, serum creatinine and BUN significantly increased 12 h after operation, so this can be diagnosed as AKI. In rats of the CLP group, plasma TIMP-2 was elevated 6 h after surgery and increased with time, suggesting that plasma TIMP-2 can be used as an early marker of AKI. Histological examination of the kidneys in this group revealed destruction of the renal tubular structure, swelling of renal tubular epithelium, the disappearance of brush edge and collapse of necrotic epithelial cells, etc., and the degree of damage increased with time. Immunohistochemistry showed that TIMP-2 was expressed in rats of the CLP group at all terms of the experiment. The expression of TIMP-2 and pyroptosis-related proteins (NLRP3, IL-1β, caspase-1, and GSDMD) in the CLP group was higher than in the SO group (p<0.05) and increased with time, suggesting that pyroptosis is involved in AKI. Thus, plasma TIMP-2 is sensitive indicator for the early detection of kidney injury and can be used as an early biomarker of AKI.

Acute kidney injury and distant organ dysfunction-network system analysis

Acute kidney injury (AKI) occurs in about half of critically ill patients and associates with high in-hospital mortality, increased long-term mortality post-discharge and subsequent progression to chronic kidney disease. Numerous clinical studies have shown that AKI is often complicated by dysfunction of distant organs, which is a cause of the high mortality associated with AKI. Experimental studies have elucidated many mechanisms of AKI-induced distant organ injury, which include inflammatory cytokines, oxidative stress and immune responses. This review will provide an update on evidence of organ crosstalk and potential therapeutics for AKI-induced organ injuries, and present the new concept of a systemic organ network to balance homeostasis and inflammation that goes beyond kidney-crosstalk with a single distant organ.

Role of the Gut Microbiota in Children with Kidney Disease

Disruption of the composition and structure of the gut microbiota, namely dysbiosis, dictates the pathophysiology of kidney diseases. The bidirectional kidney-gut axis is of interest in chronic kidney disease (CKD); the uremic milieu leads to intestinal dysbiosis and gut microbial metabolites and toxins implicated in the loss of kidney function and increased comorbidity burden. Considering that kidney diseases can originate in childhood or even earlier in fetal life, identification of the pathogenetic connection between gut microbiota dysbiosis and the development of pediatric renal diseases deserves more attention. This review concentrates on the pathogenic link between dysbiotic gut microbiota and pediatric renal diseases, covering CKD, kidney transplantation, hemodialysis and peritoneal dialysis, and idiopathic nephrotic syndrome. Gut microbiota-targeted therapies including dietary intervention, probiotics, prebiotics, postbiotics and fecal microbial transplantation are discussed for their potential for the treatment of pediatric renal diseases. A deeper understanding of gut microbiota in pediatric renal diseases will aid in developing innovative gut microbiota-targeted interventions for preventing or attenuating the global burden of kidney diseases.

MicroRNAs in septic acute kidney injury

Sepsis is a potentially fatal complication of burns and trauma that can cause acute kidney injury (AKI) with substantial morbidity and mortality, but this disease is poorly understood. Despite medical advances, effective therapeutic regimens for septic AKI remain uncommon. MicroRNAs (miRNAs) are endogenous non-coding RNAs that influence the translation of target messenger RNAs in a variety of biological processes. Emerging evidence has shown that miRNAs are intimately associated with septic AKI. The goal of this review was to summarize recent advances in the profound understanding of the functional role of miRNAs in septic AKI, as well as to provide new insights into miRNAs as feasible biomarkers and therapeutic targets for septic AKI.

Is compromised intestinal barrier integrity responsible for the poor prognosis in critically ill patients with pre-existing hyperglycemia?

BACKGROUND

Compromised intestinal barrier integrity can be independently driven by hyperglycemia, and both hyperglycemia and intestinal barrier injury are associated with poor prognosis in critical illness. This study investigated the intestinal barrier biomarkers in critically ill patients, to explore the role of compromised intestinal barrier integrity on the prognosis of critically ill patients with pre-existing hyperglycemia.

METHODS

This was a retrospective observational study. The relationships between intestinal barrier biomarkers and glycated hemoglobin A1c (HbA1c), fasting blood glucose (FBG), indicators of clinical characteristics, disease severity, and prognosis in critically ill patients were investigated. Then the metrics mentioned above were compared between survivors and non-survivors, the risk factors of 90-day mortality were investigated by logistic regression analysis. Further, patients were divided into HbA1c < 6.5% Group and HbA1c ≥ 6.5% Group, metrics mentioned above were compared between these two groups.

RESULTS

A total of 109 patients with critical illness were included in the study. D-lactate and lipopolysaccharide (LPS) were associated with sequential organ failure assessment (SOFA) score and 90-day mortality. LPS was an independent risk factor of 90-day mortality. DAO, NEU (neutrophil) proportion, temperature, lactate were lower in HbA1c ≥ 6.5% Group while D-lactate, LPS, indicators of disease severity and prognosis showed no statistical difference between HbA1c < 6.5% Group and HbA1c ≥ 6.5% Group.

CONCLUSIONS

Intestinal barrier integrity is associated with the disease severity and prognosis in critical illness. Compromised intestinal barrier integrity might be responsible for the poor prognosis in critically ill patients with pre-existing hyperglycemia.

Organ Crosstalk in Acute Kidney Injury: Evidence and Mechanisms

Acute kidney injury (AKI) is becoming a public health problem worldwide. AKI is usually considered a complication of lung, heart, liver, gut, and brain disease, but recent findings have supported that injured kidney can also cause dysfunction of other organs, suggesting organ crosstalk existence in AKI. However, the organ crosstalk in AKI and the underlying mechanisms have not been broadly reviewed or fully investigated. In this review, we summarize recent clinical and laboratory findings of organ crosstalk in AKI and highlight the related molecular mechanisms. Moreover, their crosstalk involves inflammatory and immune responses, hemodynamic change, fluid homeostasis, hormone secretion, nerve reflex regulation, uremic toxin, and oxidative stress. Our review provides important clues for the intervention for AKI and investigates important therapeutic potential from a new perspective.

Intestinal Injury Biomarkers Predict Mortality in Pediatric Severe Malaria

Severe malaria (SM) increases the risk of invasive bacterial infection, and there is evidence to suggest increased gastrointestinal permeability. Studies have shown sequestration of infected erythrocytes in intestinal microvasculature, and in vivo studies of rectal mucosa have demonstrated disruption of microvascular blood flow. However, the extent of intestinal injury in pediatric malaria is not well characterized. In this study, two serum biomarkers of intestinal injury, trefoil factor 3 (TFF3) and intestinal fatty acid binding protein (I-FABP), were analyzed in 598 children with SM and 120 healthy community children (CC), 6 months to 4 years of age. Serum was collected at enrollment and 1 month for laboratory studies, and participants were monitored for 12 months. Intestinal injury biomarkers were significantly elevated in children with SM, with 18.1% having levels of TFF3 and/or I-FABP greater than the 99th percentile of CC levels. TFF3 levels continued to be elevated at 1 month, while I-FABP levels were comparable to CC levels. Both markers predicted in-hospital mortality {odds ratio (OR) (95% confidence interval [CI]), 4.4 (2.7, 7.3) and 2.3 (1.7, 3.1)} for a natural log increase in TFF3 and I-FABP, respectively. TFF3 was also associated with postdischarge mortality (OR, 2.43 [95% CI, 1.1, 4.8]). Intestinal injury was associated with acute kidney injury (AKI), acidosis (P < 0.001 for both), and angiopoietin 2, a maker of endothelial activation. In conclusion, intestinal injury is common in pediatric severe malaria and is associated with an increased mortality. It is strongly associated with AKI, acidosis, and endothelial activation. IMPORTANCE In children with severe malaria, intestinal injury is a common complication associated with increased mortality. Intestinal injury is associated with acute kidney injury, acidosis, and endothelial activation. Interventions promoting intestinal regeneration and repair represent novel approaches to improve outcomes.

Sepsis and Acute Kidney Injury: A Review Focusing on the Bidirectional Interplay

Although sepsis and acute kidney injury (AKI) have a bidirectional interplay, the pathophysiological mechanisms between AKI and sepsis are not clarified and worthy of a comprehensive and updated review. The primary pathophysiology of sepsis-associated AKI (SA-AKI) includes inflammatory cascade, macrovascular and microvascular dysfunction, cell cycle arrest, and apoptosis. The pathophysiology of sepsis following AKI contains fluid overload, hyperinflammatory state, immunosuppression, and infection associated with kidney replacement therapy and catheter cannulation. The preventive strategies for SA-AKI are non-specific, mainly focusing on infection control and preventing further kidney insults. On the other hand, the preventive strategies for sepsis following AKI might focus on decreasing some metabolites, cytokines, or molecules harmful to our immunity, supplementing vitamin D3 for its immunomodulation effect, and avoiding fluid overload and unnecessary catheter cannulation. To date, several limitations persistently prohibit the understanding of the bidirectional pathophysiologies. Conducting studies, such as the Kidney Precision Medicine Project, to investigate human kidney tissue and establishing parameters or scores better to determine the occurrence timing of sepsis and AKI and the definition of SA-AKI might be the prospects to unveil the mystery and improve the prognoses of AKI patients.

Genetic Deletion of LRP5 and LRP6 in Macrophages Exacerbates Colitis-Associated Systemic Inflammation and Kidney Injury in Response to Intestinal Commensal Microbiota

Extraintestinal manifestations are common in inflammatory bowel disease and involve several organs, including the kidney. However, the mechanisms responsible for renal manifestation in inflammatory bowel disease are not known. In this study, we show that the Wnt-lipoprotein receptor-related proteins 5 and 6 (LRP5/6) signaling pathway in macrophages plays a critical role in regulating colitis-associated systemic inflammation and renal injury in a murine dextran sodium sulfate-induced colitis model. Conditional deletion of the Wnt coreceptors LRP5/6 in macrophages in mice results in enhanced susceptibility to dextran sodium sulfate colitis-induced systemic inflammation and acute kidney injury (AKI). Furthermore, our studies show that aggravated colitis-associated systemic inflammation and AKI observed in LRP5/6^LysM mice are due to increased bacterial translocation to extraintestinal sites and microbiota-dependent increased proinflammatory cytokine levels in the kidney. Conversely, depletion of the gut microbiota mitigated colitis-associated systemic inflammation and AKI in LRP5/6^LysM mice. Mechanistically, LRP5/6-deficient macrophages were hyperresponsive to TLR ligands and produced higher levels of proinflammatory cytokines, which are associated with increased activation of MAPKs. These results reveal how the Wnt-LRP5/6 signaling in macrophages controls colitis-induced systemic inflammation and AKI.

Acute Kidney Injury and Intestinal Dysbiosis

Within the multiple communication pathways of the intestine-kidney axis, one of the most important pathways is the interaction between the commensals of the intestinal microbiome, through the production of short-chain fatty acids, and the segments of the nephron. These interactions maintain a perfect environmental balance. During AKI, there are negative repercussions in all organs, and the systemic interconnection is related in part to the intense inflammation and the uremic environment that this syndrome generates. For example, in the intestine, the microbiome is severely affected, with a decrease in benign bacteria that promote anti-inflammatory effects and an increase in negative, pro-inflammatory bacteria. This scenario of intestinal dysbiosis widens the inflammatory loop that favors worsening kidney function and the probability of dying. It is possible that the manipulation of the intestinal microbiome with probiotics, prebiotics and symbiotics is a reasonable therapeutic goal for AKI.

Polymyxin B-Associated Nephrotoxicity and Its Predictors: A Retrospective Study in Carbapenem-Resistant Gram-Negative Bacterial Infections

Polymyxin B (PMB), a kind of polymyxin, was widely used in carbapenem-resistant Gram-negative bacterial (CR-GNB) infections. However, adverse reactions such as nephrotoxicity and neurotoxicity limit its use in clinical practice. The aim of this study was to explore PMB associated with nephrotoxicity and its predictors. Patients who received PMB intravenous drip for more than 72 h were eligible for the study. Characteristics of patients, concomitant nephrotoxic agents, underlying disease, and antimicrobial susceptibility were submitted for descriptive analysis. Univariate analysis and binary logistic regression were used to assess the factors leading to acute kidney injury (AKI). AKI was assessed with serum creatinine variations according to the classification of risk (stage R), injury (stage I), failure (stage F), loss, and end-stage of kidney disease. Among 234 patients with CR-GNB infections who used PMB in our study, 67 (28.63%) patients developed AKI, including 31 (14.25%) patients in stage R, 15 (6.41%) patients in stage I, and 21 (8.97%) patients in stage F. The incident rate of PMB-related nephrotoxicity in patients with normal renal function was 32.82% (43/131). The higher risk factors of AKI include males [odds ratio (OR) = 3.237; 95% confidence interval (95%CI) = 1.426–7.350], digestive system diseases [OR = 2.481 (1.127–5.463)], using furosemide (&gt;20 mg/day) [OR = 2.473 (1.102–5.551)], and baseline serum creatinine [OR = 0.994 (0.990–0.999)]. Nonparametric tests of K-independent samples showed that baseline serum creatinine and the PMB maintenance dose were associated with the severity of nephrotoxicity (both p &lt; 0.05). Male, digestive system diseases, using furosemide (&gt;20 mg/day), and high baseline serum creatinine were the independent risk factors of PMB-associated AKI development. The maintenance dose of PMB may be related to the severity of AKI. These risk factors should be taken into consideration when initiating PMB-based therapy. The serum creatinine value should be closely monitored when using PMB.

Intestinal microbiota dysbiosis in acute kidney injury: novel insights into mechanisms and promising therapeutic strategies

In recent years, the clinical impact of intestinal microbiota–kidney interaction has been emerging. Experimental evidence highlighted a bidirectional evolutionary correlation between intestinal microbiota and kidney diseases. Nonetheless, acute kidney injury (AKI) is still a global public health concern associated with high morbidity, mortality, healthcare costs, and limited efficient therapy. Several studies on the intestinal microbiome have improved the knowledge and treatment of AKI. Therefore, the present review outlines the concept of the gut–kidney axis and data about intestinal microbiota dysbiosis in AKI to improve the understanding of the mechanisms of the intestinal microbiome on the modification of kidney function and response to kidney injury. We also introduced the future directions and research areas, emphasizing the intervention approaches and recent research advances of intestinal microbiota dysbiosis during AKI, thereby providing a new perspective for future clinical trials.

Acute Kidney Injury and Gut Dysbiosis: A Narrative Review Focus on Pathophysiology and Treatment

Acute kidney injury (AKI) and gut dysbiosis affect each other bidirectionally. AKI induces microbiota alteration in the gastrointestinal (GI) system, while gut dysbiosis also aggravates AKI. The interplay between AKI and gut dysbiosis is not yet well clarified but worthy of further investigation. The current review focuses on the pathophysiology of this bidirectional interplay and AKI treatment in this base. Both macrophages and neutrophils of the innate immunity and the T helper type 17 cell from the adaptive immunity are the critical players of AKI-induced gut dysbiosis. Conversely, dysbiosis-induced overproduction of gut-derived uremic toxins and insufficient generation of short-chain fatty acids are the main factors deteriorating AKI. Many novel treatments are proposed to deter AKI progression by reforming the GI microbiome and breaking this vicious cycle. Data support the benefits of probiotic treatment in AKI patients, while the results of postbiotics are mainly limited to animals. Prebiotics and synbiotics are primarily discussed in chronic kidney disease patients rather than AKI patients. The effect of adsorbent treatment seems promising, but more studies are required before the treatment can be applied to patients. Immune therapy and some repurposed drugs such as allopurinol are prospects of future treatments and are worth more discussion and survey.

Hydrogen: A Novel Treatment Strategy in Kidney Disease

BACKGROUND

Hydrogen is a chemical substance that has yet to be widely used in medicine. However, recent evidence indicates that hydrogen has multi-faceted pharmacological effects such as antioxidant, anti-inflammatory, and antiapoptotic properties. An increased number of studies are being conducted on the application of hydrogen in various diseases, especially those affecting the renal system.

SUMMARY

Hydrogen can be inhaled, as a gas or liquid, and can be administered orally, intravenously, or locally. Hydrogen can rapidly enter suborganelles such as mitochondria and nucleus by simple diffusion, producing reactive oxygen species (ROS) and triggering DNA damage. Hydrogen can selectively scavenge hydroxyl radical (•OH) and peroxynitrite (ONOO^-), but not other reactive oxygen radicals with physiological functions, such as peroxyanion (O₂^-) and hydrogen peroxide (H₂O₂). Although the regulatory effect of hydrogen on the signal transduction pathway has been confirmed, the specific mechanism of its influence on signal molecules remains unknown. Although many studies have investigated the therapeutic and preventive effects of H₂ in cellular and animal experiments, clinical trials are few and still far behind. As a result, more clinical trials are required to investigate the role of hydrogen in kidney disease, as well as the effect of its dose, timing, and form on the overall efficacy. Large-scale randomized controlled clinical trials will be required before hydrogen can be used to treat renal illnesses.

KEY MESSAGES

This article reviews the mechanisms of hydrogen in the treatment of renal disease and explores the possibilities of its use in clinical practice.

LncRNA TCONS_00145741 Knockdown Prevents Thrombin-Induced M1 Differentiation of Microglia in Intracerebral Hemorrhage by Enhancing the Interaction Between DUSP6 and JNK

Background: The differentiation of microglia from M1 to M2 exerts a pivotal role in the aggression of intracerebral hemorrhage (ICH), and long non-coding RNAs (lncRNAs) are associated with the differentiation of microglia. However, the underlying mechanism had not been fully clarified.

Methods: The expression profile of lncRNAs in thrombin-induced primary microglia was analyzed by RNA sequencing. Under thrombin treatment, the effect of lncRNA TCONS_00145741 on the differentiation of microglia was determined by immunofluorescence staining, quantitative real-time PCR, and Western blot. The potential mechanism and related signaling pathways of TCONS_00145741 in the M1 and M2 differentiation of microglia in ICH were assessed by Gene Ontology analysis, flow cytometry, RNA pull-down, RNA Immunoprecipitation, and RNA fluorescence in situ hybridization followed by immunofluorescence analysis.

Results: LncRNA TCONS_00145741 expression was elevated in the thrombin-induced primary microglia, and the interference with TCONS_00145741 restrained the M1 differentiation of microglia and facilitated the M2 differentiation under thrombin treatment. The interference with TCONS_00145741 restrained the activation of the JNK pathway in microglia under thrombin treatment and repressed the JNK phosphorylation levels by enhancing the interaction between DUSP6 and JNK. In vivo experiments further illustrated that the interference with TCONS_00145741 alleviated ICH.

Conclusion: LncRNA TCONS_00145741 knockdown prevented thrombin-induced M1 differentiation of microglia in ICH by enhancing the interaction between DUSP6 and JNK. This study might provide a promising target for the clinical treatment of ICH.

Microbe defines the efficacy of chemotherapeutic drug: a complete paradigm

The human body harbors a diverse microbiome that regulates host physiology and disease development. Several studies have also been reported where the human microbiome interferes with the efficacy of chemotherapeutics. Reports have also suggested the use of microbes in specific targeting and drug delivery. This review mainly focuses on the alteration in the efficacy of the drug by human microbiota. We have also discussed how the diversity in microbes can determine the therapeutic outcomes of a particular drug. The pathways involved in the alteration are also focused, with some highlights on microbes being used in cancer therapy.

Large animal models for translational research in acute kidney injury

While extensive research using animal models has improved the understanding of acute kidney injury (AKI), this knowledge has not been translated into effective treatments. Many promising interventions for AKI identified in mice and rats have not been validated in subsequent clinical trials. As a result, the mortality rate of AKI patients remains high. Inflammation plays a fundamental role in the pathogenesis of AKI, and one reason for the failure to translate promising therapeutics may lie in the profound difference between the immune systems of rodents and humans. The immune systems of large animals such as swine, nonhuman primates, sheep, dogs and cats, more closely resemble the human immune system. Therefore, in the absence of a basic understanding of the pathophysiology of human AKI, large animals are attractive models to test novel interventions. However, there is a lack of reviews on large animal models for AKI in the literature. In this review, we will first highlight differences in innate and adaptive immunities among rodents, large animals, and humans in relation to AKI. After illustrating the potential merits of large animals in testing therapies for AKI, we will summarize the current state of the evidence in terms of what therapeutics have been tested in large animal models. The aim of this review is not to suggest that murine models are not valid to study AKI. Instead, our objective is to demonstrate that large animal models can serve as valuable and complementary tools in translating potential therapeutics into clinical practice.

HMGB1 signaling-regulated endoplasmic reticulum stress mediates intestinal ischemia/reperfusion-induced acute renal damage

BACKGROUND

Ischemia/reperfusion of the intestine often leads to distant organ injury, but the mechanism of intestinal ischemia/reperfusion-induced renal dysfunction is still not clear. The present study aimed to investigate the mechanisms of acute renal damage after intestinal ischemia/reperfusion challenge and explore the role of released high-mobility group box-1 in this process.

METHODS

Intestinal ischemia/reperfusion was induced in male Sprague-Dawley rats by clamping the superior mesenteric artery for 1.5 hours. At different reperfusion time points, anti-high-mobility group box-1 neutralizing antibodies or ethyl pyruvate were administered to neutralize or inhibit circulating high-mobility group box-1, respectively.

RESULTS

Significant kidney injury was observed after 6 hours of intestinal reperfusion, as indicated by increased serum levels of urea nitrogen and creatinine, increased expression of neutrophil gelatinase-associated lipocalin, interleukin-6, and MIP-2, and enhanced cell apoptosis, as indicated by cleaved caspase 3 levels in renal tissues. The levels of phosphorylated eIF2ɑ, activating transcription factor 4, and C/EBP-homologous protein (CHOP) were markedly elevated, indicating the activation of endoplasmic reticulum stress in the impaired kidney. High-mobility group box-1 translocated to cytoplasm in the intestine and serum concentrations of high-mobility group box-1 increased notably during the reperfusion phase. Both anti-high-mobility group box-1 antibodies and ethyl pyruvate treatment significantly reduced serum high-mobility group box-1 concentrations, attenuated endoplasmic reticulum stress in renal tissue and inhibited the development of renal damage. Moreover, the elevated expression of receptor for advanced glycation end products in the kidneys after intestinal ischemia/reperfusion was abrogated after high-mobility group box-1 inhibition.

CONCLUSION

These results suggested that high-mobility group box-1 signaling regulated endoplasmic reticulum stress and promoted intestinal ischemia/reperfusion-induced acute kidney injury. High-mobility group box-1 neutralization/inhibition might serve as a pharmacological intervention strategy for these pathophysiological processes.

Significance of the Gut Microbiota in Acute Kidney Injury

Recent studies have revealed that the gut microbiota plays a crucial role in maintaining a healthy, as well as diseased condition. Various organs and systems, including the kidney, are affected by the gut microbiota. While the impacts of the gut microbiota have been reported mainly on chronic kidney disease, acute kidney injury (AKI) is also affected by the intestinal environment. In this review, we discussed the pathogenesis of AKI, highlighting the relation to the gut microbiota. Since there is no established treatment for AKI, new treatments for AKI are highly desired. Some kinds of gut bacteria and their metabolites reportedly have protective effects against AKI. Current studies provide new insights into the role of the gut microbiota in the pathogenesis of AKI.

Integrated Fecal Microbiome and Serum Metabolomics Analysis Reveals Abnormal Changes in Rats with Immunoglobulin A Nephropathy and the Intervention Effect of Zhen Wu Tang

Immunoglobulin A nephropathy (IgAN), an autoimmune renal disease with complicated pathogenesis, is one of the principal reasons for end-stage renal disease in the clinic. Evidence has linked apparent alterations in the components of the microbiome and metabolome to renal disease in rats. However, thus far, there is insufficient evidence that supports the potential relationship between gut microbiome, circulating metabolites, and IgAN. This study was designed to probe the effects of IgAN on intestinal microecology and metabolic phenotypes and to understand the possible underlying mechanisms. Fecal and serum samples were collected from IgAN rats. Composition of the gut microbiota and biochemical changes in the metabolites was analyzed using 16S rDNA sequencing and untargeted metabolomics. The IgAN rats exhibited renal insufficiency and increased concentration of 24-h urine protein, in addition to deposition of IgA and IgG immune complexes in the kidney tissues. There was a disturbance in the balance of gut microbiota in IgAN rats, which was remarkably associated with renal damage. Marked changes in microbial structure and function were accompanied by apparent alterations in 1,403 serum metabolites, associated with the disorder of energy, carbohydrate, and nucleotide metabolisms. Administration of Zhen Wu Tang ameliorated microbial dysbiosis and attenuated the renal damage. Besides, treatment with Zhen Wu Tang modulated the metabolic phenotype perturbation in case of gut microbiota dysbiosis in IgAN rats. In conclusion, these findings provided a comprehensive understanding of the potential relationship between the intestinal microbiota and metabolic phenotypes in rats with IgAN. Elucidation of the intestinal microbiota composition and metabolic signature alterations could identify predictive biomarkers for disease diagnosis and progression, which might contribute to providing therapeutic strategies for IgAN.

Clinical utility of characterizing intestinal flora in septic kidney injury

The incidence of septic acute kidney injury (AKI) is increasing, it has become a major threat to human health because of its acute onset, poor prognosis, and high hospital costs. The most common cause of AKI in critical-care units is sepsis. Septic AKI is a complex and multi-factorial process; its pathogenesis is not fully understood. In sepsis, the destruction of mucosal barriers, intestinal flora disorders, intestinal ischemia/reperfusion injury, use of antibiotics, and lack of intestinal nutrients lead to an inflammatory reactions that in turn affects the metabolism and immunity of the host. Such changes further influence the occurrence and development of AKI. New technology is enabling various detection methods for intestinal flora. Clinical application of these methods in septic renal injury is expected to clarify the relationship among pathogenesis, disease progression mechanism, and intestinal flora.

Kidney-gut crosstalk in renal disease

INTRODUCTION

The colon has an important role in managing nitrogenous waste products, electrolytes, and mineral balance during kidney diseases. However, colonic microbiota produces uremic toxins, such as indoxyl sulfate and p-cresyl sulfate, in chronic kidney disease (CKD) patients, which due to their proinflammatory properties contribute to CKD progression. Conversely, in acute renal injury patients, intestinal microbiota could reduce inflammation by secreting short-chain fatty acids and inducing a renal protective immune response. However, since the intestines are the most frequently affected organ in advanced sepsis, colonic microbiota can also represent a negative factor for kidney health in this scenario.

CONCLUSION

In the present review, the main characteristics of kidney-gut crosstalk are described.

Distal organ inflammation and injury after resuscitative endovascular balloon occlusion of the aorta in a porcine model of severe hemorrhagic shock

BACKGROUND AND OBJECTIVE

Resuscitative Endovascular Balloon Occlusion of Aorta (REBOA) has emerged as a potential life-saving maneuver for the management of non-compressible torso hemorrhage in trauma patients. Complete REBOA (cREBOA) is inherently associated with the burden of ischemia reperfusion injury (IRI) and organ dysfunction. However, the distal organ inflammation and its association with organ injury have been little investigated. This study was conducted to assess these adverse effects of cREBOA following massive hemorrhage in swine.

METHODS

Spontaneously breathing and consciously sedated Sinclair pigs were subjected to exponential hemorrhage of 65% total blood volume over 60 minutes. Animals were randomized into 3 groups (n = 7): (1) Positive control (PC) received immediate transfusion of shed blood after hemorrhage, (2) 30min-cREBOA (A30) received Zone 1 cREBOA for 30 minutes, and (3) 60min-cREBOA (A60) given Zone 1 cREBOA for 60 minutes. The A30 and A60 groups were followed by resuscitation with shed blood post-cREBOA and observed for 4h. Metabolic and hemodynamic effects, coagulation parameters, inflammatory and end organ consequences were monitored and assessed.

RESULTS

Compared with 30min-cREBOA, 60min-cREBOA resulted in (1) increased IL-6, TNF-α, and IL-1β in distal organs (kidney, jejunum, and liver) (p < 0.05) and decreased reduced glutathione in kidney and liver (p < 0.05), (2) leukopenia, neutropenia, and coagulopathy (p < 0.05), (3) blood pressure decline (p < 0.05), (4) metabolic acidosis and hyperkalemia (p < 0.05), and (5) histological injury of kidney and jejunum (p < 0.05) as well as higher levels of creatinine, AST, and ALT (p < 0.05).

CONCLUSION

30min-cREBOA seems to be a feasible and effective adjunct in supporting central perfusion during severe hemorrhage. However, prolonged cREBOA (60min) adverse effects such as distal organ inflammation and injury must be taken into serious consideration.

Gut-organ axis: a microbial outreach and networking

Human gut microbiota (GM) includes a complex and dynamic population of microorganisms that are crucial for well-being and survival of the organism. It has been reported as diverse and relatively stable with shared core microbiota, including Bacteroidetes and Firmicutes as the major dominants. They are the key regulators of body homeostasis, involving both intestinal and extra-intestinal effects by influencing many physiological functions such as metabolism, maintenance of barrier homeostasis, inflammation and hematopoiesis. Any alteration in GM community structures not only trigger gut disorders but also influence other organs and cause associated diseases. In recent past, the GM has been defined as a 'vital organ' with its involvement with other organs; thus, establishing a link or a bi- or multidirectional communication axis between the organs via neural, endocrine, immune, humoral and metabolic pathways. Alterations in GM have been linked to several diseases known to humans; although the exact interaction mechanism between the gut and the organs is yet to be defined. In this review, the bidirectional relationship between the gut and the vital human organs was envisaged and discussed under several headings. Furthermore, several disease symptoms were also revisited to redefine the communication network between the gut microbes and the associated organs.

Csf2 Attenuated Sepsis-Induced Acute Kidney Injury by Promoting Alternative Macrophage Transition

Sepsis is a systemic inflammatory state that occurs in response to infection and significantly increases mortality in combination with acute kidney injury (AKI). Macrophages accumulate in the kidney after injury and undergo a transition from a proinflammatory (M1) phenotype to an alternatively activated (M2) phenotype that is required for normal repair. However, the specific signals that regulate the transition from the M1 to M2 phenotype in vivo are unknown. Here, we found an unexpected role of Colony stimulating factor 2 (Csf2) in controlling macrophage transition in vitro and in a mouse model of sepsis induced by cecal ligation and puncture (CLP). We first co-cultured human M1 macrophages with HK-2 cells and characterized cytokine/chemokine profiles via Luminex. Of the cytokines and chemokines that were overexpressed in medium from M1 macrophages cocultured with human kidney-2 (HK-2) cells compared with that from M1 macrophages cultured alone, Csf2 and IL6 showed the greatest increases. Csf2 was exclusively secreted by HK-2 cells but not by M1 macrophages. Furthermore, recombinant human Csf2 protein promoted transition of M1 macrophages to the M2 phenotype in a dose and time-dependent manner. The apoptosis and reactive oxygen species (ROS) release induced by M1 macrophages in HK-2 cells was attenuated after exposure to exogenous Csf2. In addition, the switch from the proinflammatory M1 phenotype to the M2 phenotype occurred via the p-Stat5 pathway, which was activated by Csf2. Importantly, we found that intraperitoneal injection of a Csf2-neutralizing antibody after CLP aggravated kidney injury and suppressed tubular proliferation, subsequently decreasing survival. However, administration of recombinant mouse Csf2 protein could rescue mice with sepsis. Together, our results indicate that Csf2 plays critical roles in regulating macrophage transition via activation of p-STAT5. These data form a foundation upon which new therapeutic strategies can be designed to improve the therapeutic efficacy of cytokine-based treatments for sepsis-induced AKI.

Pathophysiological Mechanisms by which Heat Stress Potentially Induces Kidney Inflammation and Chronic Kidney Disease in Sugarcane Workers

BACKGROUND

Chronic kidney disease of non-traditional origin (CKDnt) is common among Mesoamerican sugarcane workers. Recurrent heat stress and dehydration is a leading hypothesis. Evidence indicate a key role of inflammation.

METHODS

Starting in sports and heat pathophysiology literature, we develop a theoretical framework of how strenuous work in heat could induce kidney inflammation. We describe the release of pro-inflammatory substances from a leaky gut and/or injured muscle, alone or in combination with tubular fructose and uric acid, aggravation by reduced renal blood flow and increased tubular metabolic demands. Then, we analyze longitudinal data from >800 sugarcane cutters followed across harvest and review the CKDnt literature to assess empirical support of the theoretical framework.

RESULTS

Inflammation (CRP elevation and fever) and hyperuricemia was tightly linked to kidney injury. Rehydrating with sugary liquids and NSAID intake increased the risk of kidney injury, whereas electrolyte solution consumption was protective. Hypokalemia and hypomagnesemia were associated with kidney injury.

DISCUSSION

Heat stress, muscle injury, reduced renal blood flow and fructose metabolism may induce kidney inflammation, the successful resolution of which may be impaired by daily repeating pro-inflammatory triggers. We outline further descriptive, experimental and intervention studies addressing the factors identified in this study.

Microbiome-Metabolome Signature of Acute Kidney Injury

Intestinal microbiota play a considerable role in the host’s organism, broadly affecting its organs and tissues. The kidney can also be the target of the microbiome and its metabolites (especially short-chain fatty acids), which can influence renal tissue, both by direct action and through modulation of the immune response. This impact is crucial, especially during kidney injury, because the modulation of inflammation or reparative processes could affect the severity of the resulting damage or recovery of kidney function. In this study, we compared the composition of rat gut microbiota with its outcome, in experimental acute ischemic kidney injury and named the bacterial taxa that play putatively negative or positive roles in the progression of ischemic kidney injury. We investigated the link between serum creatinine, urea, and a number of metabolites (acylcarnitines and amino acids), and the relative abundance of various bacterial taxa in rat feces. Our analysis revealed an increase in levels of 32 acylcarnitines in serum, after renal ischemia/reperfusion and correlation with creatinine and urea, while levels of three amino acids (tyrosine, tryptophan, and proline) had decreased. We detected associations between bacterial abundance and metabolite levels, using a compositionality-aware approach—Rothia and Staphylococcus levels were positively associated with creatinine and urea levels, respectively. Our findings indicate that the gut microbial community contains specific members whose presence might ameliorate or, on the contrary, aggravate ischemic kidney injury. These bacterial taxa could present perspective targets for therapeutical interventions in kidney pathologies, including acute kidney injury.

Gut microbiota in surgical and critically ill patients

Microbiota-defined as a collection of microbial organisms colonising different parts of the human body-is now recognised as a pivotal element of human health, and explains a large part of the variance in the phenotypic expression of many diseases. A reduction in microbiota diversity, and replacement of normal microbes with non-commensal, pathogenic or more virulent microbes in the gastrointestinal tract-also known as gut dysbiosis-is now considered to play a causal role in the pathogenesis of many acute and chronic diseases. Results from animal and human studies suggest that dysbiosis is linked to cardiovascular and metabolic disease through changes to microbiota-derived metabolites, including trimethylamine-N-oxide and short-chain fatty acids. Dysbiosis can occur within hours of surgery or the onset of critical illness, even without the administration of antibiotics. These pathological changes in microbiota may contribute to important clinical outcomes, including surgical infection, bowel anastomotic leaks, acute kidney injury, respiratory failure and brain injury. As a strategy to reduce dysbiosis, the use of probiotics (live bacterial cultures that confer health benefits) or synbiotics (probiotic in combination with food that encourages the growth of gut commensal bacteria) in surgical and critically ill patients has been increasingly reported to confer important clinical benefits, including a reduction in ventilator-associated pneumonia, bacteraemia and length of hospital stay, in small randomised controlled trials. However, the best strategy to modulate dysbiosis or counteract its potential harms remains uncertain and requires investigation by a well-designed, adequately powered, randomised controlled trial.

Change of surfactant protein D and A after renal ischemia reperfusion injury

Acute kidney injury (AKI) is associated with widespread effects on distant organs, including the lungs. Surfactant protein (SP)-A and SP-D are members of the C-type lectin family, which plays a critical role in host defense and regulation of inflammation in a variety of infections. Serum levels of SP-A and SP-D are markers to reflect lung injury in acute respiratory distress syndrome, idiopathic pulmonary fibrosis, and sarcoidosis. We investigated the change of lung-specific markers, including SP-A and SP-D in an AKI mice model. We studied C57BL/6J mice 4 and 24 hours after an episode of ischemic AKI (23 min of renal pedicle clamping and then reperfusion); numerous derangements were present, including SP-A, SP-D, and lung tight-junction protein. Neutrophil infiltration and apoptosis in the lungs increased in ischemic AKI. Receptor for advanced glycation end products (RAGE) in the lungs, a marker of pneumocyte I, was not changed. Lung tight-junction proteins, particularly claudin-4, claudin-18, and anti-junctional adhesion molecule 1 (JAMA-1), were reduced in 24 hours after AKI. Serum SP-A and SP-D significantly increased in ischemic AKI. SP-A and SP-D in the lungs did not increase in ischemic AKI. The immunohistochemistry showed that the expression of SP-A and SP-D was intact in ischemic AKI. SP-A and SP-D in the kidneys were significantly higher in AKI than in the sham. These patterns of SP-A and SP-D in the kidneys were similar to those of serum. AKI induces apoptosis and inflammation in the lungs. Serum SP-A and SP-D increased in ischemic AKI, but these could have originated from the kidneys. So serum SP-A and SP-D could not reflect lung injury in AKI. Further study is needed to reveal how a change in lung tight-junction protein could influence the prognosis in patients with AKI.

Aerosol inhalation of a hydrogen-rich solution restored septic renal function

Sepsis-related acute kidney injury (AKI) is known to be caused by inflammation. We explored the renal protective effects of aerosol inhalation of a hydrogen-rich solution (HRS; hydrogen gas dissolved to saturation in saline) in a mouse model of septic AKI. Septic AKI was induced through 18 hours of cecal ligation and puncture. AKI occurred during the early stage of sepsis, as evidenced by increased blood urea nitrogen and serum creatinine levels, pathological changes, renal fibrosis and renal tubular epithelial cell apoptosis, accompanied by macrophage infiltration and M1 macrophage-associated pro-inflammatory cytokine (Il-6 and Tnf-α) generation in renal tissues. Aerosol inhalation of the HRS increased anti-inflammatory cytokine (Il-4 and Il-13) mRNA levels in renal tissues and promoted macrophage polarization to the M2 type, which generated additional anti-inflammatory cytokines (Il-10 and Tgf-β). Ultimately, aerosol inhalation of HRS protected the kidneys and increased survival among septic mice. HRS was confirmed to promote M2 macrophage polarization in lipopolysaccharide-stimulated RAW 264.7 cells. The TGF-β1 receptor inhibitor SB-431542 partly reversed the effects of HRS on renal function, fibrosis, tubular epithelial cell apoptosis and senescence in mice. Thus, HRS aerosol inhalation appears highly useful for renal protection and inflammation reduction in septic AKI.